1. Field of the Invention
The invention is concerned with the field of semiconductor electronics. It is based on a method for the production of a gate turn-off thyristor having an anode-side stop layer and a transparent anode emitter in accordance with the preamble of the first claim.
2. Discussion of Background
EP 0 621 640 A1 has already described such a method and a gate turn-off thyristor (GTO) produced thereby. A transparent anode emitter is understood to mean an anode-side emitter layer which is configured in such a way that a significant proportion of the total current leaves the anode metallization layer of the component as an electron current. This electron current, which is specified in % of the total current, is referred to as the emitter transparency. Anode emitters having a transparency of 50% or more are technologically important. A transparent emitter of the generic type is obtained, for example, by selecting a layer depth of 1.2 .mu.m and indiffusing a doping concentration of 10.sup.18 cm.sup.-3. Further transparent anode emitters are disclosed in the documents EP 0 651 445 A2 and EP 0 700 095 A2.
On account of the good properties of GTOs having a stop layer and a transparent anode emitter, ever more transparent, i.e. thinner and less heavily doped, anode emitters are desired. However, an ever thinner and more weakly doped anode emitter leads to considerable technological difficulties in the production of the metallic contact of the anode electrode with the anode emitter. When the aluminum is deposited on the semiconductor, the silicon is dissolved and condenses out again on cooling down. This means that the anode emitter is greatly influenced by the metallization process. Subsequent sintering, as is customary in other GTOs for the purpose of reducing the contact resistance, is virtually impossible.